1. Technical Field
The present invention relates to a system of a plurality of series-connected fuel cell converter devices and a method for controlling the system. More particularly, the present invention relates to a system and a method for charging and discharging via a plurality of series-connected fuel cell converter devices.
2. Description of Related Art
Electricity, which has been indispensable to the daily lives of humans since the Industrial Revolution, is generated nowadays mainly by thermal or nuclear power. However, as both of these power generation methods have adverse impacts on the environment, and given the increasing abnormalities in today's global climate, it is imperative to generate electricity by alternative means.
Fuel cells generate electricity through chemical reactions, which do not produce substances harmful to the environment, and therefore fuel cells have been an important developing trend in power generation technology. For instance, a conventional fuel cell-based power generation system typically includes three major parts: a fuel cell stack for generating electricity, a converter for converting the unstable electricity generated by the fuel cell stack into a stable power source for output, and a battery for providing electricity in conjunction with the fuel cell stack when the fuel cell stack alone is insufficient to cope with an increase in the load, wherein the battery stops supplying electricity as soon as the power generated by the fuel cell stack meets the load requirement.
The aforesaid conventional fuel cell-based power generation system is disadvantageous in that the electricity generated by the fuel cell stack will not be output when the converter is damaged, which is extremely inconvenient. Moreover, a desired increase in the output power of the fuel cell stack is not achieved until chemical reactions in the fuel cell stack are completed. Therefore, if the load increases abruptly and goes beyond the capacity of the battery, a shortage of power supply is bound to occur, and the load will be affected as a result.
In addition, when fuel is added to the fuel cell stack, the chemical reactions of the added fuel will upset the stability of the output power temporarily, which is likely to damage the load.